A Method for determining safe concentrations of chloride ions in pitting corrosion of steels in nitrate media

Razygraev, V. P.; Lebedeva, M. V.; Korchak, I.I.

doi:10.1134/s0033173208070163

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…The self-passivation of Fe-Mn-Al steels containing Al or Al-Cr was attributed to the autocatalytic nature of HNO 3 reduction as proposed elsewhere [27,28]. Accordingly, this behaviour, a spontaneous active-passive transition in some Fe-Mn-Al steels, is logical in the light of the autocatalytic nature of HNO 3 reduction to the oxidant NO 2 , as shown in Equation 1:…”

Section: Electrochemical Polarization Behaviourmentioning

confidence: 93%

NITRIC ACID RESISTANCE OF NEW TYPE Fe-Mn-Al STAINLESS STEELS

Hamada¹,

Karjalainen²

2006

Canadian Metallurgical Quarterly

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Several high-Mn (25-30 wt%) Fe-Mn-Al alloys containing various Al and Cr levels with fully austenitic or duplex microstructures have been studied. The effect of the alloying elements such as Al and Al-Cr on the passivation mechanism in 5-50% HNO 3 solutions was investigated by using electrochemical measurements, X-ray diffraction and scanning electron microscopy. The results of anodic polarization scans showed that the acid corrosion resistance of Fe-30Mn-4Al-4Cr and Fe-30Mn-8Al-6Cr alloys is superior to that of alloys without Cr. The X-ray analysis confirmed the presence of Al 2 O 3 and Cr 2 O 3 in the passive film. Scanning electron microscopy showed that the formation of the passive film takes place by the direct nucleation and growth mechanism. It is apparent that the corrosion resistance of Fe-Mn-Al steels is not dependent on their phase structure but rather on the chemical composition. Comparing with AISI 304 stainless steel, the passive film that formed on Fe-Mn-Al alloys bearing high Al and Cr, was found to be more stable in 5-50% HNO 3 solutions.Résumé -On a étudié plusieurs alliages de Fe-Mn-Al à haute teneur en Mn (25-30% en poids) contenant des niveaux variés d'Al et de Cr, à microstructure complètement austénitique ou duplex. On a étudié l'effet des éléments d'alliage comme l'Al et Al-Cr sur le mécanisme de passivation dans des solutions de 5-50% HNO 3 en utilisant des mesures électrochimiques, la diffraction des rayons x et la microscopie électronique à balayage. Les résultats de balayages de polarisation anodique ont montré que la résistance à la corrosion acide des alliages Fe-30Mn-4Al-4Cr et Fe-30Mn-8Al-6Cr était supérieure à celle d'alliages sans Cr. L'analyse de rayons x a confirmé la présence d'Al 2 O 3 et de Cr 2 O 3 dans la couche passivante. La microscopie électronique à balayage a montré que la formation de la couche passivante se faisait par le mécanisme de nucléation directe et de croissance. Il est apparent que la résistance à la corrosion des aciers Fe-Mn-Al ne dépend pas de la structure de phase mais plutôt de la composition chimique. Comparant à l'acier inoxydable AISI 304, on a trouvé que la couche passivante qui s'est formée sur les alliages Fe-Mn-Al à teneur élevée en Al et en Cr était plus stable dans des solutions de 5-50% HNO 3 .

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Section: Electrochemical Polarization Behaviourmentioning

confidence: 93%

NITRIC ACID RESISTANCE OF NEW TYPE Fe-Mn-Al STAINLESS STEELS

Hamada¹,

Karjalainen²

2006

Canadian Metallurgical Quarterly

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“…6 The liquid radioactive waste is mainly alkaline, consisting of NaNO 2 , concentrated NaNO 3 and sometimes a relatively small amount of chloride. 1,[6][7][8][9][10][11] Nitrite has been reported to inhibit corrosion of alloys, [12][13][14][15][16] while nitrate was regarded as either a corrosion inhibitor [17][18][19][20][21][22] or an aggressive species. 6,[23][24][25] Several hypotheses of LAI corrosion in this environment have been proposed, which include increase of aggressive chloride concentration due to evaporation, 2,26 ohmic potential drop due to crevice-like meniscus geometry, 6,27 and depletion of OH − due to CO 2 from air.…”

mentioning

confidence: 99%

Liquid-Air Interface Corrosion of A537 Steel in High Level Liquid Radioactive Waste Simulant in a Sealed Container

Xu¹,

Zhang²,

Yang³

et al. 2019

J. Electrochem. Soc.

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Liquid-air interface (LAI) corrosion is regarded as a potential issue for interim storage tanks of high level liquid radioactive waste. Insightful studies have been carried out and several hypotheses have been proposed so far, while none has been directly confirmed experimentally. A sealed container has been developed to investigate the effect of atmosphere on LAI corrosion of partially immersed A537 steels, in which the composition and temperature of air can be changed accordingly, i.e. CO 2 concentration varied between 0.05 wt% (natural air) and 1.97 wt%, and temperature varied between 25 • C and 34 • C. It has been found that the pitting initiation process under both anodic polarization and free immersion conditions can be largely accelerated by the increase of CO 2 concentration. More importantly, a planar pH electrode has been applied to measure pH at the interface during anodic polarization and free immersion, and the occurrence of LAI corrosion can be correlated with the same interface pH at a certain temperature regardless of CO 2 concentration, indicating a "critical pH" for LAI corrosion determined by this method. This finding suggests that LAI corrosion in high level liquid radioactive waste may be investigated through determination of a critical pH in certain circumstances.

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“…5 This information is significant both in the field of electrochemical machining (ECM), where nitrate solutions are often used, [6][7][8] and in corrosion of steel in radioactive waste solutions. [9][10][11] These salt layers are a slurry of crystallites that form on a dissolving metal surface 12 when the rate of metal ion production (dissolution) is greater than the rate that they can diffuse from the interface, leading to supersaturation and thus crystallite nucleation. The equilibrium thickness of the layer is determined by a self-regulating process.…”

mentioning

confidence: 99%

In-situ Synchrotron Studies of the Effect of Nitrate on Iron Artificial Pits in Chloride Solutions

Street

Amri

et al. 2015

J. Electrochem. Soc.

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The effect of nitrate on the salt layers in iron artificial corrosion pits in acidic chloride solutions has been studied using in-situ synchrotron X-ray diffraction. During dissolution in 1 M HCl, there is a salt layer of FeCl 2 .4H 2 O on the electrode surface, which is isotropic. With addition of trace nitrate, the salt layer remains FeCl 2 .4H 2 O and no nitrate phase is observed, but the diffraction pattern becomes anisotropic, consistent with the formation of platelets with (1 2 0) planes settling horizontally. In nitrate solution containing trace of chloride (0.1 M HNO 3 + 10 mM HCl), a salt layer is formed that is isostructural with Co(NO 3 ) 2 .6H 2 O, and therefore assumed to be Fe(NO 3 ) 2 .6H 2 O. This is the first reported crystal structure of ferrous nitrate. The salt layer is also found to give an anisotropic diffraction pattern, consistent formation of platelets with (0 2 0) It is well known that salt layers can form at the bottom of growing corrosion pits due to supersaturation of metal salts, [1][2][3][4] and that the presence of salt layers is important for continued pit growth.5 This information is significant both in the field of electrochemical machining (ECM), where nitrate solutions are often used, [6][7][8] and in corrosion of steel in radioactive waste solutions. 9-11These salt layers are a slurry of crystallites that form on a dissolving metal surface 12 when the rate of metal ion production (dissolution) is greater than the rate that they can diffuse from the interface, leading to supersaturation and thus crystallite nucleation. The equilibrium thickness of the layer is determined by a self-regulating process.

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A Method for determining safe concentrations of chloride ions in pitting corrosion of steels in nitrate media

Cited by 5 publications

References 4 publications

NITRIC ACID RESISTANCE OF NEW TYPE Fe-Mn-Al STAINLESS STEELS

NITRIC ACID RESISTANCE OF NEW TYPE Fe-Mn-Al STAINLESS STEELS

Liquid-Air Interface Corrosion of A537 Steel in High Level Liquid Radioactive Waste Simulant in a Sealed Container

In-situ Synchrotron Studies of the Effect of Nitrate on Iron Artificial Pits in Chloride Solutions

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